its hard to give you bass lines because you deknt specify a progression or a context EX shout from the 1-4 or 2-5-1 or what ever i used to play bass i am no expert but your best bet is to study the basic progressions 2-5-1 and begin to approach each chords root from a half step below then do it from above then do it from above and below then add the third and eventually the fifth and seventh get crazy and add the ninths remember the you are holding down harmony as well as rhythm so begin thinking in terms of the chord qualities make the major one chord a slash chord by playing the third or sixth under it
use this in a shout or drive going back and forth between Db and F#
Db,Eb,F,F# E,Eb,D,DB B,A,G,F#Bb,B,C
AGain without a context it is hard but i can recommend two excellent boods
the evolving bassist by rufus reid this book gets you so improvisationally ready to play any bass line over any kind of music with any kind of feel
standing in the shadows of motown
good luck